The present invention relates generally to angular position sensors.
Some motor vehicle control systems require angular position sensors that need only sense partial angular motion of one part relative to another part, e.g., less than plus or minus ninety degrees (+/xe2x88x9290xc2x0). Shaped magnets have been used in conjunction with magnetic field sensors in order to provide non-contact angular position sensors that sense partial angular motion. It happens that angular position sensors utilizing rotating magnets sensed by stationary magnet field sensors produce a sinusoidal or pseudo-sinusoidal output signal that merely approximates a linear output signal. As a result, as recognized the present invention, these sensors have limited accuracy.
Resistance-strip position sensors have also been widely used to determine the position of a moving part relative to a corresponding stationary part. The present invention understands that these traditional sensors can have reliability problems due to the susceptibility of the resistance-strips to premature wear. Moreover, the vibration of contact brushes along the resistance-strips can cause unacceptable electrical noise in the output signals.
The present invention has recognized these prior art drawbacks, and has provided the below-disclosed solutions to one or more of the prior art deficiencies.
An angular position sensor includes a rotor. A first magnet is attached to the surface of the rotor, and a second magnet is attached to the surface of the rotor opposite the first magnet. Additionally, a first concentrator is disposed around the perimeter of the rotor and a second concentrator is disposed around the perimeter of the rotor opposite the first concentrator such that a space is established between the first concentrator and the second concentrator. A magnetic field sensing element is disposed in the space established between the first concentrator and the second concentrator.
In a preferred embodiment, the magnetic field sensing element is a Hall sensor. Preferably, the rotor is coupled to a rotating element and the first concentrator and second concentrator are stationary with respect to the rotor.
In one aspect of the present invention, each magnet defines an inner pole and an outer pole. The width of the outer pole is greater than the width of the inner pole. Moreover, the concentrators are arc-shaped and span an angle of approximately one hundred and thirty degrees.
In another aspect of the present invention, each magnet defines an inner pole width and an outer pole width. The inner pole width is equal to the outer pole width. In this aspect of the present invention, each magnet has a length that is at least two times greater than the inner pole width and outer pole width. Moreover, the concentrators are arc-shaped and span an angle of approximately ninety degrees.
In yet another aspect of the present invention, a vehicle control system includes a microprocessor and an angular position sensor electrically coupled to the microprocessor. The sensor provides a linear signal to the microprocessor that represents angular motion in a range between negative ninety degrees and positive ninety degrees.